Journal of Sensor Science and Technology (센서학회지)

The Korean Sensors Society (한국센서학회)
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A Polymer-based Capacitive Air Flow Sensor with a Readout IC and a Temperature Sensor

  • Kim, Wonhyo (Smart Sensor Research Center, Korea Electronics Technology Institute) ;
  • Lee, Hyugman (Smart Sensor Research Center, Korea Electronics Technology Institute) ;
  • Lee, Kook-Nyeong (Smart Sensor Research Center, Korea Electronics Technology Institute) ;
  • Kim, Kunnyun (Smart Sensor Research Center, Korea Electronics Technology Institute)
  • Received : 2018.10.30
  • Accepted : 2019.01.30
  • Published : 2019.01.31
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Abstract

This paper presents an air flow sensor (AFS) based on a polymer thin film. This AFS primarily consists of a polymer membrane attached to a metal-patterned glass substrate and a temperature-sensing element composed of NiCr. These two components were integrated on a single glass substrate. The AFS measures changes in capacitance caused by deformation of the polymer membrane based on the air flow and simultaneously detects the temperature of the surrounding environment. A readout integrated circuit (ROIC) was also fabricated for signal processing, and an ROIC chip, 1.8 mm by 1.9 mm in size, was packaged with an AFS in the form of a system-in-package module. The total size of the AFS is 1 by 1 cm, and the diameter and thickness of the circular-shaped polymer membrane are 4 mm and $15{\mu}m$, respectively. The rate of change of the capacitance is approximately 11.2% for air flows ranging between 0 and 40 m/s.

Keywords

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Fig. 1. Schematic diagram of the structure’s capacitance

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Fig. 2. Schematic of the AFS with temperature sensor.

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Fig. 3. Fabrication process for the bottom electrode structure of the AFS

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Fig. 4. Images of the AFS fabrication process. (a) Polymer membrane as the top electrode, (b) patterned glass substrate as the bottom electrode and the assembled AFS.

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Fig. 5. Capacitance measured by the AFS due to air-flow changes in a wind channel.

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Fig. 6. Temperature characteristics of the AFS with a temperature sensor.

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Fig. 1. Simplified block diagram of the proposed ROIC for the AFS.

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Fig. 2. Operation of the airflow counting logic based on the airflow rate.

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Fig. 9. Photograph of the ROIC chip and SiP module with the AFS. (a) Chip layout (left) and fabricated ROIC (right), (b) SiP module with the AFS.

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Fig. 10. The air flow measurement system, including the control board and LCD monitor.

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